The present invention relates to a structure for adjusting the position of the magnetic heads of optomagnetic disk devices for recording signals on or reproducing signals from optomagnetic disks, and to a method of adjusting the position.
As shown in FIG. 13, optomagnetic disk devices for minidisks comprise a head support unit 20 having a magnetic head 16 and an objective lens 10 which are opposed to each other as arranged on opposite sides of an optomagnetic disk 102 serving as a recording medium, with the lens 10 provided on a pickup 12. Signals are recorded on or reproduced from the disk 102 while moving the head support unit 20 radially of the disk 102.
The pickup 12 has a laser light source incorporated therein for projecting a laser beam as converged by an objective lens on the optomagnetic disk 102. With the recording layer on the disk heated to a Curie temperature with the projected laser beam, alternating current is passed through the core of the magnetic head 16 to set up a magnetic field on the head 16, whereby the recording layer is magnetized for signal recording. Signals are reproduced from the recording layer when the pickup 12 receives the laser beam projected on the layer and reflected therefrom.
To effectively apply the magnetic field of the magnetic head to the optomagnetic disk, there is a need to align the center of the head with that of the objective lens by position adjustment.
Accordingly, the position of the magnetic head is adjusted relative to the pickup by moving the head radially and tangentially of the disk.
A head support unit 20 adapted to adjust the position of the magnetic head 16 will be described with reference to FIGS. 13 and 14, and FIG. 1 of the invention.
The pickup 12 is in engagement with a drive screw rod 54 mounted on an optomagnetic disk device 44 (see FIG. 1), and is reciprocatingly movable radially of the disk (in the directions of arrows in FIG. 1) by the screw thrust of the drive screw rod 54. Formed in one end of the pickup 12 are screw holes 22 for use in attaching a head arm 14.
The head arm 14 comprises a support piece 62 attached to a bottom wall of the pickup 12 and adjustable in position, and a head lever 64 carrying the magnetic head 16 at its forward end, mounted on the support piece 62 and adjustable in position.
The support piece 62 has slits 24 parallel to a tangential direction of the disk and positioned in corresponding relation with the screw holes 22 in the pickup 12. The pickup 12 and the support pieces 62 are held in engagement by screws 100 slidably fitting in the slits 24 and screwed in the screw holes 22, respectively. With the screws 100 loosened, the support piece 62 is slidable tangentially of the disk relative to the pickup 12. When the screws 100 are tightened up after the magnetic head 16 has been positioned in place tangentially of the disk, the heads of the screws press the support piece 62 against the pickup 12 to fix the support piece 62 to the pickup 12. A screw locking agent is applied to the screw heads for preventing the screws 100 from loosening after the screws 100 have been tightened up.
The support piece 62 is bent upward at one end thereof, and the bent portion is provided at its upper end with a bracket 68. The head lever 64 is supported by an adjusting screw 76 on the bracket 68 slidably radially of the disk and adjustably in position. The screw 76 is in screw-thread engagement with the bracket 68. A compression spring (not shown) fitted around the adjusting screw 76 for biasing the head lever 64 radially of the disk is provided between two brackets of the support piece 62 and the head lever 64. The head lever 64 is moved radially of the disk by turning the adjusting screw 76, whereby the position of the magnetic head 16 is adjusted radially of the disk. The screw locking agent is applied to the portion of the screw 76 screwed in the bracket 68 to prevent the screw 76 from rotating.
For use with conventional minidisks, the magnetic head has a relatively large core size of about 700 xcexcmxc3x97700 xcexcm, so that the position of the magnetic head is adjustable satisfactorily under a microscope if accuracy is attained to some extent. Further even if the head is somewhat shifted when the fixing screws 100 are tightened up after the position adjustment of the head, the shift is considered permissible.
Low power consumption and a high magnetic field efficiency are required of the magnetic disk device, Advanced Strage MO (trademark: AS-MO), having a superhigh resolution and proposed in recent years. Accordingly, the core size of the magnetic head of this device is as small as up to about 400 xcexcm radially of the disk and about 150 xcexcm tangentially thereof, such that satisfactory performance is no longer available if the head is positioned in place under a microscope. Especially, some magnetic heads have a core size of about 100 xcexcm tangentially of the disk, and the adjustment of the position of such a head in the disk tangential direction is of extreme importance.
However, the head support unit is so constructed that the support piece of the head arm is fastened to the pickup with the screws 100 after the position of the magnetic head has been adjusted tangentially of the disk as described above, so that the support piece 62 is likely to bend when fastened to the pickup as seen in FIG. 15 (as indicated at P in the drawing). A residual stress is then likely to remain in the support piece 62, possibly shifting the magnetic head during or after fastening. Further since the pickup 12 and head arm 14 are generally made from a metal plate by blanking, these components are each likely have a strain, with the result that the magnetic head as accurately adjusted in position will be shifted when subsequently fastened.
An object of the present invention is to provide an optomagnetic disk device having a magnetic head which can be positioned accurately especially tangentially of the magnetic disk, and a method of adjusting the position of the magnetic head.
The present invention provides an optomagnetic disk device 44 wherein a head support unit 20 comprises a pickup 12 having an objective lens 10 mounted thereon for converging a laser beam, and a head arm 14 connected to the pickup 12, the head arm 14 having one end attached to the pickup 12 and a free end provided with a magnetic head 16, the head arm 14 being adjustable in position relative to the pickup 12 so that the magnetic head 16 is opposed to the objective lens 10 on the pickup 12, the head support unit 20 being movable radially of an optomagnetic disk,
the pickup 12 having at least one screw hole 22 for attaching the head arm 14 thereto,
the head arm 14 having a slit 24 opposed to the screw hole 22 of the pickup 12 and in parallel to a tangential direction of the disk,
a screw 26 being slidably fitted in the slit 24 of the head arm 14 and having a distal end screwed in the screw hole 22 of the pickup 12,
an elastic member 30 being provided between the screw 26 and the head arm 14 for pressing the head arm 14 against the pickup 12.
For use in the optomagnetic disk device 44, the present invention provides a method of adjusting the position of the magnetic head 16 which method comprises moving the head arm 14 relative to the pickup 12 tangentially of the disk, with the head arm 14 pressed against the pickup 12 by the elastic member 30, to adjust the position of the magnetic head 16 relative to the objective lens 10 on the pickup 12 and thereafter fixing the head arm 14 to the pickup 12.
The head arm 14 as adjusted in position can be fixed to the pickup 12 by applying a screw locking agent.
Since the head arm 14 is attached to the pickup 12, as pressed against the pickup 12 by the elastic member 30, the head arm 14 can be moved tangentially of the disk by applying a force to the arm in this direction. In this state, the head arm 14 is slidingly moved tangentially of the disk to adjust the position of the magnetic head 16.
Although the position adjustment can be made, for example, under a microscope, it is desirable to make the adjustment while passing a current through the magnetic head 16 and reading the resulting output signal, if an improved accuracy is to be achieved in the case where the head 16 has a small core size as will be described later.
When the position of the magnetic head 16 has been completely adjusted, the head arm 14 is fixed to the pickup 12. The arm can be fixed by applying the screw locking agent. When thus fixed with use of the locking agent, the arm is free of shifting or residual stress that would occur when screws are tightened up for locking, and can therefore be fixed without displacing the magnetic head to accurately adjust the position of the head.